1988 300E has no heat

I just finished replacing the water pump, belt, and hoses (all of them) on
my 1988 mb 300e. It started up just fine and there seems to be no massive
leaks anywhere, however coolant is not making it to the heater core. The

circulating pump is not working and I have not yet checked to determine if
the water solenoid valve is operating. Any helpful hints/clever ways of
troubleshooting these two items would be greatly appreciated.
Thanks, Roy in Louisiana.

Make sure you have bled the coolant at the top of the thermostat housing(12mm
bolt). Add coolant until it comes out of bleed screw. Start engine and put ACC
into the defrost position. Leave the top off the expansion tank so coolant will
flow into engine. The monovalve normally fails in the open position (full heat)
so I would check the fuse for the aux coolant pump first. Run the engine at
1200-1500RPM once the temp gauge gets to 75-80C. Even witht he aux pump not
running, there should be coolant flow to the heater core.
Dick

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